Many electronic devices employ keyboards. Keyboards are configured with a standardized set of keys to enable predictable and rapid data entry, such as typing by way of a QWERTY keyboard. Conventional keyboards typically provide a uniform input force response profile for all keys. That is, the stiffness, travel, height (or other dimension) and/or damping characteristics of each key are common. Mechanical springs or other mechanical mechanisms are typically used below each key to provide the input response. Because the key response often is uniform for all keys, some users may experience fatigue in relatively weaker fingers or experience double entry of keys pressed by relatively stronger fingers. Also, some users would prefer an alternate key response based on typing speed or nominal typing input force, e.g. a less stiff keyboard or with increased damping. Furthermore, mechanical mechanisms may change properties over time or with excessive use. For example, springs fixed below keys frequently used by index fingers, typically the strongest finger of a user, may tend to wear more rapidly, causing a reduced stiffness and/or increased damping.
A user may prefer a variable key response keyboard that varies with the finger being used, key type, and/or key position, and/or an adaptable key response that adapts to a user's typing input style and does not degrade or alter response with usage. A variable response keyboard may reduce user fatigue in that the keyboard force profile may be tuned on a per-finger basis, so as to require, for example, less force for key entry for weaker fingers. The variable response keyboard controls per-key response profiles by way of magneto-rheological (MR) materials.